Fluid handling system for electrical discharge machining equipment

ABSTRACT

Electrical discharge machining equipment including a worktable reservoir tank, a fluid storage and settling tank and a source of clean fluid under pressure. Clean fluid under pressure is directed to a gap between an electrode and a workpiece in the reservoir tank during machining, Fluid is pumped between the tanks by a jet pump. Clean fluid under pressure powers the jet pump. A side arm of the jet pump can be connected to each of the tanks alternately to draw fluid therefrom. The discharge of the jet pump is connected to the other tank to discharge into the other tank.

v United States Patent [151 3,678,240 Dietrick [4 July 18, 1972 s41FLUID HANDLING SYSTEM FOR 3,435,175 3/1969 Shafler ..219/69 0 ELECTRICALDISCHARGE 3,469,057 9/1969 Maines ..2l9/69 D MACHINING EQUIPMENT PrimaryExaminer-R. F. Staubly [72] Inventor: Gerald P. Dletrlck, 523 RidgeviewDrive, Anamey pearce&schaepflklaus Florence, Ky. 41042 22 Filed: Feb.24, 1971 1 I ABSTRACT 21 1 1 31 Electrical discharge machining equipmentincluding a worktable reservoir tank, a fluid storage and settling tankand a source of clean fluid under pressure. Clean fluid under pres- [52]'S 219/69 D sure is directed to a gap between an electrode and aworkpiece [51] of B239 1/ in the reservoir tank during machining, Fluidis pumped arch... D, E between the tanks a j p p Chan under prcssurcpowers the jet pump. A side arm of the jet pump can be con- [56]References Cited nected to each of the tanks alternately to draw fluidUNITED STATES PATENTS therefrom. The discharge of the jet pump isconnected to the I other tank to discharge into the other tank.3,067,358 12/1962 De Main ..2l9/69 D X 3,390,247 6/1968 Webb ..2l9/69 D5 China, 10 Drawing Figures i FDWE! jalfll/ 4/ J a 37 zal- 1 h Z, 34 33x /9 j t 4a- :2; t

e 24/ 3 m 47 Z a 0 44 i .3 i i' Z3 l Q PATENTEU JUN 8191:

SHEET 1 OF 3 INVENTOR. GERALD P. DIETRICK A'rrQRUEYS- PATENTEBJuu 8 m2 0sum 3 OF 3 \NVENTOR. GERALD P. DIETRICK ATTOQNEYi- FLUID HANDLING SYSTEMFOR ELECTRICAL DISCHARGE MACHINING EQUIPMENT This invention relates toelectrical discharge machining equipment. More particularly, thisinvention relates to machinery for handling fluid used in electricaldischarge machining.

Electrical discharge machining is carried out by applying'a highfrequency voltage across an electrode and a closely: spaced workpiecewith an essentially non-conducting machine. fluid in the gaptherebetween. The machining fluid is caused: to flow continuouslythrough the gap between the electrode and the workpiece to entrainparticles of metal detached from the workpiece and from the electrodeand to remove these particles. The machining fluid is filtered andrecirculated. During the machining operation, a steady flow of filteredfluid through the gap is required. The machining is carried on with theworkpiece mounted in a reservoir filled sufficiently with the machiningfluid that the interacting parts of the electrode and the workpiece aresubmerged. Periodically, the supply of fluid in the reservoir must beremoved to remove particles separated from the workpiece and from theelectrode during machining, and then the supply of fluid in thereservoir must be replenished before further machining is performed.

An object of this invention is to provide a fluid filtering and storagesystem which'supplies a steady flow of filtered fluid to the gap betweenelectrode and workpiece during machining operations and in which thereis provision for removing a main supply of fluid from the reservoir andfor storing same.

A further object of this invention is to provide a vacuum filter forsuch a system in which a pump of the vacuum filter serves to supplyfiltered fluid under pressure to the electrode during machining and alsoserves to provide pumping power for pumping the main supply and astorage tank.

A further object of this invention is to provide such a system in whichonly filtered fluid passes through the pump.

Briefly, this invention provides an electrical discharge machiningsystem in which machining fluid passes through a vacuum filter. A vacuumpump draws filtered fluid from the filter and directs the filtered fluidto a clean fluid pressure storage tank. Fluid under pressure from theclean fluid pressure storage tank is directed to the electrode and isalso directed to a jet pump. A side arm of the jet pump can be connectedto a reservoir loading and unloading line and also to a used fluidstorage tank loading and unloading line. When the side arm of the jetpump is connected to the reservoir loading and unloading line, the jetdischarge is connected to the storage tank loading and unloading line,and when the side arm of the jet pump is connected to the storage tankloading and unloading line, the jetdischarge is connected to thereservoir loading and unloading line.

The above and other objects and features of the invention will beapparent to those skilled in the art to which this invention pertainsfrom the following detailed description and the drawings, in which:

FIG. 1 is a somewhat schematic perspective view, partly broken away andin section showing an electrical discharge machining device associatedwith a fluid handling and filtering system constructed in accordancewith an embodiment of this invention;

FIG. 2 is a top plan view of a pump and valving unit forming a part ofthe fluid handling and filtering system, pipe connections thereto beingshown in dashed lines, alternate positions for a handle thereof beingshown in dot-dash and double dotdash lines;

FIG. 3 is an elevational view looking in the direction of the arrows 33in FIG. 2;

FIG. 4 is an elevational view taken in the direction of the arof fluidbetween the reservoir rows 44 in FIG. 2;

FIG. 9 is a view in section taken on the line 99-in FIG. 2; and- FIG. 10is a view in side elevation, partly broken away and in section of afluid storage and settling tank which forms a part of the system showninFIG. 1.

In the following detailed'description andthe drawings, like referencecharacters indicate like parts.

In FIG. 1 is illustrated electrical discharge machining apparatus 15together with a fluid handling and. filtering system 16 constructed inaccordance with an-embodiment of this invention.

The fluid handling and filtering-systemincludes a worktable reservoirtank 17 in which a workpiece 18 is mounted. A weir 19 is mounted in thereservoir 17 over which machining fluid 21 can overflow into an endchamber 22 from which the overflowing fluid is drained through a line 23which discharges into a vacuum filter 24 where the fluid passes througha filter material web 26. The filter 24 can be of the type shown ingreater detail in my applicationSer. No. 14,521 filed Feb. 26, 1970. Thefilter material web 26 is supplied from a roll 261 and passes throughthe filter with an openwork conveyor 262. The conveyor is advanced asneeded by operation of a drive motor 263. Used filter material iscollected in a hopper 264. From the filter 24, the filtered fluid ispumped by a pump 27 through a line 28 to clear fluid pressure storagetanks 29-31 where the clear fluid is stored under pressure. The storagetanks 29-31 are provided with air spaces 291-311 above the liquid, andcompression of air in the air spaces serves to maintain pressure in thetanks 29-31. Lower end portions of the tanks 29-31 are connected by aline 292. When needed, liquid is discharged from the pressure storagetanks 29- 31 through a pressure line 33. The line 33 is connected to ashut-off valve 34, and the shut-off valve 34 is connected to a line 36which leads to an electrode 37. The electrode 37 is held in position byany suitable means, not shown, so that an appropriate gap may bemaintained between the operative end 38 of the electrode 37 and theworkpiece 18 during the machining operations. Electric power is suppliedfrom an appropriate power source through power leads 39 and 41 connectedto the workpiece 18 and the electrode 37, respectively.

During machining, a level of fluid 42 is maintained in the reservoir 17which overlies the interacting portions of the workpiece l8 and of theelectrode 37, and, preferably, the entire workpiece 18 is submerged. Thefluid surrounding the workpiece and the operative portion of theelectrode can be drained from the reservoir through a line 44 and a pumpand valving unit 46 to a line 47 which discharges into a used fluidstorage and settling tank 48- When the fluid is drained from thereservoir 17, particles of material removed from the workpiece 18 andfrom the electrode 37 during machining travel with the fluid to bepermitted to settle to the bottom of the storage tank 48 as a sludge 51as indicated in FIG. 10. The sludge 51 can be withdrawn from the storagetank 48 through a valve 52. A bottom plate 48' of the storage tank 48slopes toward the valve 52 to direct the sludge thereto. An overflowline 53 directs excess fluid from the storage and settling tank 48 tothe filter 24, as shown in FIG. 1.

Supernatant fluid in the storage tank 48, although unfiltered andinsufficiently clean to be directed to the gap between the electrode andthe workpiece, is sufiiciently clean for use in filling the reservoir 17surrounding the workpiece l8, and, when a new machining operation is tobe undertaken, the supernatant fluid is withdrawn from the storage andsettling tank 48 through a dip tube portion 54 of the line 47 to thepump and valving unit 46. The unit 46 pumps this fluid back through theline 44 to the reservoir 17.

Details of construction of the pump and valving unit 46 are shown inFIGS. 2-9 inclusive. The unit 46 includes a body block 56. Fluid underpressure from the pressure line 33 is directed to the unit 46 through aline 58 to a jet fitting 59 which is mounted in a threaded opening 61(FIGS. 7 and 9) in a wall 62 of the block 56. The line 44 is connectedto an inlet fitting 63 (FIG. 2). The line 47 is connected to an inletfitting 64.

The jet fitting 59 is directed into a generally venturi-shaped bore 65(FIGS. 7 and 9) in the block 56. An upright side arm bore 66 (FIG. 9)communicates with a jet chamber 66 in the block 56 surrounding the jetfitting 59 and with the venturishaped bore 65. The jet fitting 59, theventuri-shaped bore 65 and the side arm bore 66 form a jet pump orejector. The outlet end of the venturi-shaped bore 65 communicates withan upright bore 67. Flow through the unit 46 is controlled by balldiverter valve members 68 and 69 (FIG. mounted in the upright bores 66and 67 respectively. The ball valve members are similar in construction,and only the ball valve member 68 will be described in detail. As shownin FIG. 6, the ball valve member 68 includes an upright blind bore 71and a transverse blind bore 72 which meet at a hollow interior of theball valve member 68. The ball is mounted between resilient sealing ringmembers 73 and 74, which are mounted in a transverse bore 75 in theblock 56 which intersects the side arm bore 66. The ring member 73 isheld against a shoulder 76 in the bore 75 by the ball 68. A tube member77 holds the ring member 74 in engagement with the ball 68. The tubemember 77 is integral with and communicates with the interior of theinlet fitting 64. Appropriate screw fasteners 79 (FIGS. 2 and 4) holdthe tube member 77 in position inside a counterbore portion 75' of thebore 75 (FIG. 6). An opening 80 (FIG. 5) in the tube member 77 providescommunication with a lengthwise bore 80' in the block 56. A sealing ring81 forms a seal between the block 56 and the inlet fitting 64. Atransverse bore portion 82 provides communication between the inletfitting 63 and the ring member 73. The inlet fitting 63 is held inposition on the block 56 overlying the bore portion 82 by fasteners 821.A sealing ring 822 forms a seal between the inlet fitting 63 and theblock 56. The ball member 68 carries a stem 84 on which a handle 86 ismounted. The stem extends upwardly through a bore 861 in the block 56. Asealing ring 862 forms a seal between the stem 84 and the block 56. Thehandle 86 and the ball valve member can be turned from the position atwhich the handle is shown in full lines in FIG. 2 and there iscommunication between the inlet fitting 63 and the side arm bore 66, andintermediate position shown in double dot-dash lines at which theupright bores 66 and 67 are closed by the ball valve members 68 and 69,respectively and an alternate operative position at which the handle isshown in dot-dash lines and the inlet fitting 64 is in communicationwith the side arm bore 66.

The ball valve member 69 is mounted at the upper end of the upright bore67 and centrally of a transverse bore 88 (FIG. 5). One end portion ofthe bore 88 communicates with the inlet fitting 63 by means of alengthwise bore 89. The other end portion of the bore 88 is counterboredat 88' and communicates with the inlet fitting 64 by means of thelengthwise bore 80. The ball valve member 69 is mounted betweenresilient ring members 91 and 92. The ring member 92 is held inengagement with the ball valve member 69 by a cup member 95. An opening96 in a wall 97 of the cup member 95 provides communication between thelengthwise bore 80' and the ball valve member 69. Screw fasteners 99hold the cup member 95 in position in the counterbore 881. A sealingring 101 provides a seal between the cup member 95 and the block 56.

As shown in FIG. 9, a spur gear 102 is mounted on the stem 84 of theball valve member 68. A spur gear 103 is mounted on a stem 104 of theball valve member 69. The gears 102 and 103 are keyed to the stems 84and 104, respectively, by appropriate keys, not shown. An idle gear 106is mounted on a stub shaft 107 and meshes with the spur gears 102 and103 so that the spur gears 102 and 103 and the ball valve members 68 and69 turn together.

When the ball valve members are in the position shown in FIGS. 2-9inclusive, the side arm bore '66 (FIG. '6) is in communication with theinlet fitting 63, and fluid is drawn in through the line 44 (FIG. 2) tobe removed from the reservoir 17 (FIG. 1) and fluid from theventuri-shaped bore 65 (FIG. 9) passes upwardly through the upright bore67, through the ball valve member 69 to the interior of the cup member95 (FIG. 8) and throu h the opening 96 (FIG. 5) in the wall of ber 5,along the lengthwise bore and the cup mem through the opening 80 in thetube member 77 to the inlet fitting 64 to be discharged through theinlet fitting 64 and the line 47 (FIG. 2) to the storage and settlingtank 48 (FIG. I). When the handle 86 (FIG. 2) is in the intermediate(double dot-dash line) position of (FIG. 2), the ball valve members arein closed position, and there is no flow through the unit 56.

When the handle 86 is in the alternate operative (dot-dash line)position of FIG. 2, the ball valve member 68 is open to the inletfitting 64 and the ball valve member 69 is open to the inlet fitting 63(See FIG. 5). As fluid from the jet fitting 59 is injected into theventuri-shaped bore 65, fluid from the line 47 and the storage andsettling tank 48 is drawn in through the inlet fitting 64 to passthrough the ball valve member 68 and down the side arm bore 66 and to becarried through the upright bore 67, the ball valve member 69, thetransverse bore portion 88 and the lengthwise bore 89 to the inletfitting 63 through which the fluid is discharged through the line 44 tothe worktable reservoir 17.

The fluid handling system for electrical discharge machining illustratedin the drawings and described above is subject to structuralmodification without departing from the spirit and scope of the appendedclaims.

Having described my invention, what I claim as new and desire to secureby letters patent is:

1. The combination of electrical discharge machining equipment includinga worktable reservoir tank, a fluid storage and settling tank, a sourceof clean fluid under pressure, and means for directing the clean fluidunder pressure to a gap between an electrode and a workpiece in thereservoir tank during machining, with means for pumping fluid betweenthe tanks which comprises a jet pump, means for directing the cleanfluid under pressure into the jet pump to power same, means forconnecting a side arm of the jet pump to one of the tanks to draw fluidtherefrom, and means for connecting the discharge of the jet pump to theother tank to discharge into the other tank, whereby fluid is pumpedfrom one tank to the other tank.

2. A combination as in claim 1 wherein there is valve means foralternately connecting the tanks to the side arm and to the discharge ofthe jet pump for pumping fluid alternately from one tank to the othertank.

3. A combination as in claim 1 wherein means is provided forinterrupting flow of clean fluid to the jet pump while fluid is beingdelivered to the gap during machining.

4. A combination as in claim 1 wherein the source of clean fluid underpressure includes a vacuum filter and a pump for withdrawing clean fluidfrom the filter, and overflowing fluid from the tanks is directed to thefilter, the pump delivering the clean fluid under pressure.

5. A combination as in claim 4 wherein the clean fluid under pressurefrom the vacuum pump is directed to a clean fluid pressure storage tankand the clean fluid pressure storage tank supplies fluid under pressureto the gap and to the fluid directing means.

1. The combination of electrical discharge machining equipment including a worktable reservoir tank, a fluid storage and settling tank, a source of clean fluid under pressure, and means for directing the clean fluid under pressure to a gap between an electrode and a workpiece in the reservoir tank during machining, with means for pumping fluid between the tanks which comprises a jet pump, means for directing the clean fluid under pressure into the jet pump to power same, means for connecting a side arm of the jet pump to one of the tanks to draw fluid therefrom, and means for connecting the discharge of the jet pump to the other tank to discHarge into the other tank, whereby fluid is pumped from one tank to the other tank.
 2. A combination as in claim 1 wherein there is valve means for alternately connecting the tanks to the side arm and to the discharge of the jet pump for pumping fluid alternately from one tank to the other tank.
 3. A combination as in claim 1 wherein means is provided for interrupting flow of clean fluid to the jet pump while fluid is being delivered to the gap during machining.
 4. A combination as in claim 1 wherein the source of clean fluid under pressure includes a vacuum filter and a pump for withdrawing clean fluid from the filter, and overflowing fluid from the tanks is directed to the filter, the pump delivering the clean fluid under pressure.
 5. A combination as in claim 4 wherein the clean fluid under pressure from the vacuum pump is directed to a clean fluid pressure storage tank and the clean fluid pressure storage tank supplies fluid under pressure to the gap and to the fluid directing means. 